In a gas water heater, the water heating and temperature control system typically includes a combustion chamber located beneath a water tank and a gas heating element in the combustion chamber. The flow of gas to the combustion chamber is controlled by a gas valve assembly. The gas valve may include an elongate temperature probe assembly configured to sense the temperature of water in the water tank. The temperature probe assembly typically includes an invar rod disposed within a copper tube, and is often assembled to the gas valve assembly such that the temperature probe assembly protrudes from the gas valve assembly at roughly a right angle to a longitudinal axis of the gas valve assembly.
The temperature sensing probe is assembled to valve components, which are configured to open or close the flow of gas in a particular channel of the gas valve. Generally, the copper tube and invar rod assembly are configured to be positioned inside the water tank. The copper tube, having a high thermal coefficient of expansion, expands and contracts as the water temperature in the tank increases and decreases, respectively. The expansion and contraction of the copper tube acts to move the invar rod. Typically, as the water in the tank cools, the invar rod contracts and, by contracting, pushes against a lever, which causes the gas valve to allow the main gas or bleed gas to flow to the outlet of the valve and into the combustion chamber.
While regulated gas valves are common in the U.S., in some countries, it is more common to have unregulated gas valves. These unregulated gas valves typically include a gas cock to regulate the flow of gas into the valve, and a temperature adjustment knob to select a desired temperature setting. However, these unregulated gas valves do not typically have a safety feature to prevent the flow of gas to the valve in the event of a fire. Moreover, the use of two controls (i.e., the gas cock and temperature control knob) to operate the gas valve adds to both the parts cost and the assembly cost of the gas valve. And with two controls, there are two potential points of failure. As such, reducing the number of controls required to operate the unregulated gas valve could improve the reliability of the valve.
It would therefore be desirable to have an unregulated gas valve that combines the two gas valve controls into one control to save parts and assembly costs and improve reliability. It would also be desirable to have a gas valve that includes a safety feature that can prevent the flow of gas into the valve if the control knob is exposed to a fire.
Embodiments of the invention provide such an unregulated gas valve. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.